1. Field of the Invention
The present invention relates generally to an ink-jet printing apparatus, more particularly to an ink-jet printing apparatus performing the printing by ejecting an ink from a printing head toward a printing medium.
2. Description of the Related Art
Conventionally, in an ink-jet printing apparatus performing the printing by ejecting an ink from an ink ejection opening of a printing head toward a printing medium, means for protecting the ejection opening and the ejection recovery processing means are provided for solving the problems of plugging of the ink ejecting opening portion of the printing head due to the drying or ejection failure of the ink due to the dart, the bubble or the like within the ink ejection opening.
Here, throughout the disclosure, the words "ejection recovery" represents not only for resolving of the problem of the ejection failure but also, in the broader sense, for maintaining appropriately the ejection performance of the ink in the ink ejection opening of the printing head.
Major construction of such ink ejection protecting means is a cap formed with an elastic material, such as rubber or the like. The cap covers an ejection opening forming surface formed on the printing head (hereinafter occasionally referred to simply as "head"). Major construction and function of the ejection recovery processing means is to suck air within the cap by a vacuum generating means, such as a pump or the like to reduce the pressure therein for causing the forced discharge of the ink through the ejection opening and whereby to resolve the problem of the ejection failure of the ink.
Furthermore, another ejection recovery means is a preparatory ejection process for ejecting the ink from the head for a predetermined times for elimination of cause of the ejection failure. In this preparatory ejection process, it is typical to use the cap as a receptacle for ejected ink. The reason is that, by using the existing cap as the receptacle, it becomes unnecessary to provide special ink receptacle means to permit down-sizing by space saving or cost-down.
Furthermore, as a mechanism for moving the cap between an open condition (a condition moved away from the ejection opening forming surface of the head) and a closed condition (a condition where the head and the ejection opening forming surface are in contact), it is typical to pivot the cap about a cap supporting member or a pivot center. Advantage of employment of the method set forth above is that the down-sizing is possible and the high precise control of the relative position between the ejection opening forming surface of the head and the cap can be easily performed.
Furthermore, when the relatively high precision is required in the positional relationship between the cap and the head in order to certainly cover the ejection opening forming surface of the head with the cap and certainly maintaining sealing ability with the ejection opening forming surface, it is possible to provide a relative positioning means respectively for a head unit (including a carriage and so on) and a cap unit (including the cap supporting member and so on). As one example, the relative positioning of the cap and the head can be certainly performed by providing a positioning boss in the cap supporting member and a positioning hole, in which the positioning boss is inserted, in the carriage.
However, when the conventional method is used, in order to place the cap in an open condition, namely in a condition where the cap unit is placed away from the head unit, a necessary magnitude of pivoting of the cap supporting member inherently becomes large. Particularly, when a projection, such as a boss-shaped projection or the like is provided as the positioning means, this tendency becomes significant to hinder the down-sizing of the printing apparatus.
Another reason is that the accurate positioning is difficult unless the posture of the cap upon the positioning is in a parallel position to the posture of the cap in the capping position.